For producing a highly integrated semiconductor device, the following steps are generally performed. Namely, on an element such as a silicon wafer, an electro-conductive film such as a metal film to become a wiring material for electrical conduction, and an interlayer dielectric film for the sake of insulation between electro-conductive films are formed, and then on a surface thereof a photoresist is coated homogeneously to form a photosensitive layer, which is then subjected to selectively exposure and development treatments to form a desired resist pattern. Then using the resist pattern as a mask an interlayer dielectric film is subjected to a dry etching treatment to form a desired pattern in the film. Thereafter, the resist pattern and a residue generated by a dry etching treatment (hereinafter referred to as “dry etching residue”) are completely removed by oxygen plasma ashing or with a cleaning liquid.
As the result of advances in shrinkage in a design rule in recent years, RC delay is becoming a determining factor of the limit of high speed arithmetic processing. Consequently, an electro-conductive wiring material is shifting from aluminum to copper, which has lower electrical resistance, and because of this an interlayer dielectric film is shifting from a silicon oxide film to a low-dielectric constant film (a film with a relative dielectric constant of 3 or less, hereinafter referred to as “low-k film”). Further, for preventing copper from diffusing into an interlayer dielectric film, the copper is covered with a metal (hereinafter referred to as “barrier metal”), such as tantalum, and tantalum nitride, and a dielectric film (hereinafter referred to as “barrier dielectric film”), such as silicon nitride, and silicon carbide. Moreover, between a photoresist and an interlayer dielectric film, a film, which has a planarization function by filling a gap, such as ruggedness and a groove in a front end device, an absorption function of radiation reflected from a device, and a maintenance function of the shape of an interlayer dielectric film during dry etching for facilitating high precision microfabrication, has come to use. As such a film, there is, for example, an organosiloxane thin film containing a light absorption compound (hereinafter referred to as “organosiloxane thin film”). In the case of a pattern of 0.2 μm or less, for a resist with a film thickness of 1 μm, the aspect ratio of the pattern (ratio of resist film thickness divided by resist line width) becomes too high, and there arises a drawback that the pattern may collapse. To overcome the drawback, a hard mask method may be applied, by which a Ti-based or Si-based film (hereinafter referred to as “hard mask”) may be inserted between a resist film and a pattern film to be formed actually so that a resist pattern is once transcribed to the hard mask by dry etching, and then the pattern is transcribed again to the film to be formed actually by dry etching using the hard mask as an etching mask. By the method, a gas for etching a hard mask and a gas for etching a film to be formed actually may be different, therefore for etching a hard mask a gas which can exhibit high selectivity with respect to a resist, and for etching an actual film a gas which can exhibit high selectivity with respect to a hard mask can be selected, and there is an advantage that a pattern can be formed with a thin resist. Further, tungsten is used for a contact plug which establishes a connection with a substrate.
However, when an organosiloxane thin film or a photoresist is removed by an oxygen plasma, there is a risk that a low-k film existing under an organosiloxane thin film may be damaged due to exposure to an oxygen plasma, etc. For example, in the case of patterning by a via first dual damascene process, there occurs a problem that a low-k film near a via is damaged and as the result the electrical property is extremely deteriorated, when an organosiloxane thin film filled in a via is removed by an oxygen plasma. Meanwhile, since a dry etching residue is stuck to a wafer in a removal step for an organosiloxane thin film, a dry etching residue must be removed at the same time with removal of an organosiloxane thin film or a photoresist. Therefore, for production of a semiconductor device using a low-k film, a method by which an organosiloxane thin film and a photoresist are removed to the same extent as by an oxygen plasma process, and at the same time a dry etching residue can be removed, while damages to a low-k film, copper, a barrier metal, and a barrier dielectric film are suppressed, has been demanded. Further, in some cases where the method is applied to a layer with an exposed contact plug, suppression of damage to tungsten is also required. Similarly, in a case where a hard mask is used, damage to a hard mask must be also suppressed.
In Patent Literature 1, a wiring forming method with a stripping/cleaning liquid containing a quaternary ammonium hydroxide, a water-soluble organic solvent, water, an anticorrosive, and potassium hydroxide is proposed.
In Patent Literature 2, a wiring forming method with a stripping/cleaning liquid containing a quaternary ammonium hydroxide, a water-soluble organic solvent, water, an anticorrosive, potassium hydroxide, and a specific imidazole derivative, which is a cleaning liquid superior in a corrosion suppression function on tungsten, is proposed.
In Patent Literature 3, a photoresist stripping method of a printed wiring board with a stripping liquid composed of an aqueous solution containing a quaternary ammonium hydroxide, a water-soluble amine, and a hydroxyamine and azoles anticorrosive, is proposed. As an example of azoles, pyrazole is presented. In Patent Literature 3, it is described that not only pyrazole but also 1-methyl-1H-benzotriazole is effective for corrosion protection of copper.
In Patent Literature 4, a resist stripping liquid containing a water-soluble amine and/or ammonium hydroxide, an oxidation agent, and water, and usable for a copper wiring is proposed, and as an example of a corrosion prevention agent for copper, etc. pyrazole is presented. In Patent Literature 4, it is further described that not only pyrazole but also a combination of benzotriazole, or tolyltriazole with ethanol is effective for corrosion protection of copper.
In Patent Literature 5, a resist stripping liquid containing an amine, a solvent, a strong alkali, and water, and usable for a copper wiring is proposed, and as an amine pyrazole is presented. In Patent Literature 5, it is further described that not only pyrazole but also ethanol amine is effective for corrosion protection of copper.
In Patent Literature 6, an etching solution for an etching resist for a copper-clad laminate containing nitric acid, a chlorate, an iron ion, and a copper inhibitor is proposed, and as an anticorrosive for copper pyrazole is presented. In Patent Literature 6, it is further described that not only pyrazole but also benzotriazole is effective for corrosion protection of copper.
In Patent Literature 7 and Patent Literature 8, a cleaning liquid which removes an etching residue of a semiconductor device provided with a copper wiring, and is composed of an aqueous solution containing nitric acid, sulfuric acid, a fluorine compound, and a basic compound is proposed, and as the basic compound pyrazole is presented.
In Patent Literature 9, an electrolytic stripping agent for silver containing an oxyacid having a carboxyl group and one or more hydroxy groups in a molecule, or a salt thereof as a main component is proposed, and as a discoloration prevention agent for copper, which is a treatment target, pyrazoles are presented. In Patent Literature 9, it is further described that not only pyrazole but also benzotriazole is effective for corrosion protection of copper.